Timothy S. Griffin

Rotation and Cover Crop Effects on Soilborne Potato Diseases, Tuber Yield, and Soil Microbial Communities

Seven different 2-year rotations, consisting of barley/clover, canola, green bean, millet/rapeseed, soybean, sweet corn, and potato, all followed by potato, were assessed over 10 years (1997-2006) in a long-term cropping system trial for their effects on the development of soilborne potato diseases, tuber yield, and soil microbial communities. These same rotations were also assessed with and without the addition of a fall cover crop of no-tilled winter rye (except for barley/clover, for which underseeded ryegrass was substituted for clover) over a 4-year period. Canola and rapeseed rotations consistently reduced the severity of Rhizoctonia canker, black scurf, and common scab (18 to 38% reduction), and canola rotations resulted in higher tuber yields than continuous potato or barley/clover (6.8 to 8.2% higher). Addition of the winter rye cover crop further reduced black scurf and common scab (average 12.5 and 7.2% reduction, respectively) across all rotations. The combined effect of a canola or rapeseed rotation and winter rye cover crop reduced disease severity by 35 to 41% for black scurf and 20 to 33% for common scab relative to continuous potato with no cover crop. Verticillium wilt became a prominent disease problem only after four full rotation cycles, with high disease levels in all plots; however, incidence was lowest in barley rotations. Barley/clover and rapeseed rotations resulted in the highest soil bacterial populations and microbial activity, and all rotations had distinct effects on soil microbial community characteristics. Addition of a cover crop also resulted in increases in bacterial populations and microbial activity and had significant effects on soil microbial characteristics, in addition to slightly improving tuber yield (4% increase). Thus, in addition to positive effects in reducing erosion and improving soil quality, effective crop rotations in conjunction with planting cover crops can provide improved control of soilborne diseases. However, this study also demonstrated limitations with 2-year rotations in general, because all rotations resulted in increasing levels of common scab and Verticillium wilt over time.

Effect of swine and dairy manure amendments on microbial communities in three soils as influenced by environmental conditions

Understanding the impacts of manure amendments on soil microorganisms can provide valuable insight into nutrient availability and potential crop and environmental effects. Soil microbial community characteristics, including microbial populations and activity, substrate utilization (SU) profiles, and fatty acid methyl ester (FAME) profiles, were compared in three soils amended or not amended with dairy or swine manure at two temperatures (18 and 25°C) and two soil water regimes (constant and fluctuating) in laboratory incubation assays. Soil type was the dominant factor determining microbial community characteristics, resulting in distinct differences among all three soil types and some differing effects of manure amendments. Both dairy and swine manures generally increased bacterial populations, substrate diversity, and FAME biomarkers for gram-negative organisms in all soils. Microbial activity was increased by both manures in an Illinois soil but only by dairy manure in two Maine soils. Dairy manure had greater effects than swine manure on SU and FAME parameters such as increased activity, utilization of carbohydrates and amino acids, substrate richness and diversity, and fungal FAME biomarkers. Temperature and water regime effects were relatively minor compared with soil type and amendment, but both significantly affected some microbial responses to manure amendments. Overall, microbial characteristics were more highly correlated with soil physical factors and soil and amendment C content than with N levels. These results indicate the importance of soil type, developmental history, and environmental factors on microbial community characteristics, which may effect nutrient availability from manure amendments and should be considered in amendment evaluations.

Effects of Different Potato Cropping System Approaches and Water Management on Soilborne Diseases and Soil Microbial Communities

Four different potato cropping systems, designed to address specific management goals of soil conservation, soil improvement, disease suppression, and a status quo standard rotation control, were evaluated for their effects on soilborne diseases of potato and soil microbial community characteristics. The status quo system (SQ) consisted of barley underseeded with red clover followed by potato (2-year). The soil-conserving system (SC) featured an additional year of forage grass and reduced tillage (3-year, barley/timothy-timothy-potato). The soil-improving system (SI) added yearly compost amendments to the SC rotation, and the disease-suppressive system (DS) featured diverse crops with known disease-suppressive capability (3-year, mustard/rapeseed-sudangrass/rye-potato). Each system was also compared with a continuous potato control (PP) and evaluated under both irrigated and nonirrigated conditions. Data collected over three potato seasons following full rotation cycles demonstrated that all rotations reduced stem canker (10 to 50%) relative to PP. The SQ, SC, and DS systems reduced black scurf (18 to 58%) relative to PP; SI reduced scurf under nonirrigated but not irrigated conditions; and scurf was lower in DS than all other systems. The SQ, SC, and DS systems also reduced common scab (15 to 45%), and scab was lower in DS than all other systems. Irrigation increased black scurf and common scab but also resulted in higher yields for most rotations. SI produced the highest yields under nonirrigated conditions, and DS produced high yields and low disease under both irrigation regimes. Each cropping system resulted in distinctive changes in soil microbial community characteristics as represented by microbial populations, substrate utilization, and fatty acid methyl-ester (FAME) profiles. SI tended to increase soil moisture, microbial populations, and activity, as well result in higher proportions of monounsaturated FAMEs and the FAME biomarker for mycorrhizae (16:1 ω6c) relative to most other rotations. DS resulted in moderate microbial populations and activity but higher substrate richness and diversity in substrate utilization profiles. DS also resulted in relatively higher proportions of FAME biomarkers for fungi (18:2 ω6c), actinomycetes, and gram-positive bacteria than most other systems, whereas PP resulted in the lowest microbial populations and activity; substrate richness and diversity; proportions of monounsaturated and polyunsaturated FAME classes; and fungal, mycorrhizae, and actinomycete FAME biomarkers of all cropping systems. Overall, soil water, soil quality, and soilborne diseases were all important factors affecting productivity, and cropping systems addressing these constraints improved production. Cropping system approaches will need to balance these factors to achieve sustainable production and disease management.

Manure composition affects net transformation of nitrogen from dairy manures

The plant available nitrogen (PAN) content of dairy manure is commonly calculated using concentration and availability coefficients for organic nitrogen (N) and ammonium N (NH4), but the carbon (C) fraction of the manure also influences the availability of N over time. We evaluated the interactive effect of manure C and N from nine dairy manures during a 176 days aerobic incubation. All of the manures had appreciable NH4 content, and varied widely in fibrous C. The incubation was conducted using sandy loam (coarse-loamy, mixed, frigid, Typic Haplorthod) and silt loam (fine, illitic, non-acid, frigid, Aeric Epiaquepts) soils at 25 °C and 60% water-filled pore space. There were clear differences in nitrate (NO3) accumulation over time, including manures that resulted in net nitrification and net immobilization. For both soils, the rate of nitrification at 7 and 56 days after application, and the amount of NO3 accumulated at the end of the incubation (176 days) were strongly correlated (r = −0.88) with C: NH4 and also to the ratio of neutral detergent fiber (NDF):NH4 (r = −0.90). The addition of manure C also resulted in significant net immobilization, compared to addition of mineral N fertilizer alone. These studies demonstrate that increased understanding of manure C and N interactions may lead to improved prediction of manure PAN.

Comparative Investigation of Sequentially Extracted Phosphorus Fractions in a Sandy Loam Soil and a Swine Manure

Sequential fractionation is one of the most common methods used to investigate phosphorus (P) forms in soils. The strategy can be used for evaluating bioavailability of soil P and for investigating the relationship between soil P transformation and soil development. Recently, the strategy of sequential fractionation has been used to investigate manure and compost P and their changes after application to soils. However, the physico-chemical characteristics of animal manure may differ from those of soils. Evaluation is therefore needed to determine if sequentially extracted P forms based on soil studies are applicable for manure. In this study we fractionated P in a sandy loam soil and a swine (Sus scrofa) manure with H2O, 0.5 M NaHCO3, 0.1 M NaOH, and 1.0 M HCl. The P distribution in soil was 0.2% H2O-extractable, 11% NaHCO3-extractable, 58% NaOH-extractable, 14% HCl-extractable, and 16% residual P. In contrast, P distribution in swine manure was 48% H2O-extractable, 19% NaHCO3-extractable, 18% NaOH-extractable, 11% HCl-extractable, and 3% residual P. Elemental analyses, ultraviolet (UV)/visible spectra, and Fourier-transform infrared (FT/IR) spectra revealed distinct differences in chemical composition between soil and swine manure. The NaOH fraction of soil contained 128 mmol aluminum (Al) and 5.8 mmol iron (Fe) per kg of dry matter; however, the NaOH fraction of manure contained only 8.8 mmol Al and 0.6 mmol Fe per kg of dry matter. Concentrations of calcium (Ca) and magnesium (Mg) in various fractions of manure, however, were much higher than in soil. The soil was inorganic mineral-based, and the animal manure was organic residue-based. These data indicate it may not be appropriate to apply soil based fractionation interpretations to swine manure by exclusively assigning NaOH-extractable inorganic P (Pi) to Al- and Fe-P, and HCl-extractable-Pi to Ca-P. We attribute the distinctly different P distribution patterns observed with sequential fractionation of soil and manure to their different physico-chemical properties. These differences must be recognized when developing and interpreting fractionation procedures for manure.

Evaluation Of Soil Phosphorus Transformations By Sequential Fractionation And Phosphatase Hydrolysis

Increased understanding is needed on the interconversion among P species when manure and fertilizer are added to soils. To assess changes in P species affected by manure and fertilizer addition, a sandy loam (no established soil series designation; coarseloamy, mixed, frigid, Typic Haplorthod) and a Lamoine silt loam (fine, illitic, nonacid, frigid Aeric Epiaquept) with no P added, with fertilizer P, and with dairy manures were incubated at 22 °C for up to 108 days. Sequential fractionation with H2O, 0.5 M NaHCO3, and 0.1 M NaOH and phosphatase hydrolysis were used to monitor changes in inorganic P and enzymatically hydrolyzable and nonhydrolyzable organic P during the incubation period. Similar patterns of P dynamics were observed in the two soils. Added inorganic P from either chemical fertilizer or animal manure amendments was found mainly in the NaHCO3 and NaOH fractions. Changes in H2O, NaHCO3, and NaOH-extractable P were similar for P fertilizer–amended soils and unamended soils, indicating that soil properties played a major role in controlling P dynamics. In the H2O fraction, inorganic P attained a low and stable level after an initial rapid decrease. Concentrations of P species in other fractions fluctuated during the incubation period. Furthermore, the fluctuations were observed in complementary patterns between inorganic P in the NaHCO3 and NaOH fractions as well as between labile P (inorganic and hydrolyzable organic) and nonhydrolyzable organic P in the NaOH fraction. These complementary fluctuations implied an interchange of P species during incubation. This interchange could be an important mechanism for maintaining balance between labile and immobile P in soils. Further detailed examination of the patterns of interchange among P fractions in soils may provide more accurate prediction of soil P bioavailability, thus improving soil P management.

Enzymatic hydrolysis of organic phosphorus in extracts and resuspensions of swine manure and cattle manure

Animal manure can be a valuable resource of P for plant growth. Organic phosphates (Po) are considered bioavailable if they can be hydrolyzed to inorganic P (Pi). Therefore, investigation of the susceptibility of manure Po to hydrolysis may increase our understanding of manure Po bioavailability. In this study, we demonstrate that three orthophosphate-releasing enzymes, acid phosphatase from wheat germ, alkaline phosphatase from bovine intestinal mucosa, and fungal phytase from Aspergillus ficcum, were able to hydrolyze certain amounts of Po in animal manure. A scheme of sequential enzymatic release of Po in manure was developed and then used to investigate changes in swine and cattle manure P distribution after storage at −20°C, 4°C or 22°C for about a year. Assuming that the P distribution in manure maintained at −20°C remained unchanged (i.e., similar to fresh manure), bioavailable P (Pi and enzyme-hydrolysable Po) in swine manure remained relatively constant [72.8–76.3% of total P (Pt)]. Soluble but enzymatically unhydrolysable Po (Pue) increased from 7.2% to 32.1% of Pt during storage at 4°C. In cattle manure, bioavailable P decreased from 71.6% to 62.9% of Pt, and Pue increased from 21.7% to 37.2% of Pt during storage at 22°C. These data indicated that the major change during the storage of animal manure for a year was the increase in Pue, so manure P solubility may increase with storage, but the increase would not produce more bioavailable P in the manure. The effects of storage on the bioavailability of manure P should be further investigated to develop an efficient manure-P management strategy.

SOIL PHOSPHORUS DYNAMICS IN RESPONSE TO DAIRY MANURE AND INORGANIC FERTILIZER APPLICATIONS

In modern agriculture practices, the application of plant nutrients to soil is usually required for sustained high crop yields. Manure is generally applied to meet crop N needs. The impact of N-based manure application rates on soil P transformations should therefore be evaluated for efficient utilization of both manure N and P. In this study, 11 dairy manure and inorganic fertilizers were added to two Maine soils to supply 100 mg organic N kg−1 soil. Our data showed that the general distribution patterns in manure-amended soils for three P species, inorganic P (Pi), enzymatically hydrolyzable organic P (Peo), and nonhydrolyzable organic P, basically followed the trend of changes for inorganic fertilizer amended (control) soils, indicating that soil properties played a major role in controlling P dynamics. In H2O and NaHCO3 fractions, soil bioavailable P (Pi and Peo) was linearly related to added P. However, NaOH-extractable soil P was not closely related to the P applied in the manure. This work confirmed that a single application of manure impacted soil bioavailable P in a manner similar to fertilizer and did not significantly impact soil P properties and environment. This means that growers converting from conventional to organic practices (i.e., where manure is the sole source of N and P) may estimate manure bioavailable P to meet their short-term P needs. Further studies need to be conducted to determine if similar results can be found under field conditions.

Effects of Organic Dairy Manure on Soil Phosphatase Activity, Available Soil Phosphorus, and Growth of Sorghum-Sudangrass

Abstract Organic dairy (OD) production is increasing in the Northeastern United States due to consumer demand. Some physicochemical properties of OD manure differ from conventional dairy (CD) manure, which could influence nutrient cycling and soil fertility differently when OD manure is applied as fertilizer to meet plant N demands. Effects of OD manure on activities of acid phosphomonoesterase (ACP), alkaline phosphomonoesterase (ALP), phosphodiesterase (PDE), available soil phosphorus (P), and plant growth were investigated in a greenhouse study, where sorghum-sudangrass (Sorghum bicolor subsp. drummondii) was fertilized with manures from 13 organic dairies in Maine, CD manure, or NH4NO3. Soil phosphatase activities and modified Morgan P were determined at planting and after 16 weeks of plant growth. Plant growth did not differ (P > 0.05) when fertilized with OD and CD manures or inorganic fertilizer. However, there was a wide range in growth with OD manure, which was negatively correlated to manure C:N and C:P (P < 0.05) ratios. After 16 weeks, OD manure amended soils had higher modified Morgan P than soils with inorganic fertilizer (P < 0.05), but there was no difference between OD and CD manured soils (P > 0.05). Of the three soil phosphatases, ACP activity was highest and increased with OD manure similarly to CD manure. There was a negative correlation (P < 0.01) between ACP activity and manure C:P ratio, suggesting that manure C content influences P cycling and may reduce P availability in soils amended with OD manure, in a manner similar to CD manure.

Phosphorus Mineralization and Availability in Soil Amended with Biosolids and Animal Manures

ABSTRACT Land spreading of biosolids (sewage sludge) and animal manures on agricultural soils is a means of disposal that is both environmentally and economically attractive. As with any soil amendment, there is potential for adverse impact from the land application of these materials. Applying biosolid or manure to meet crop N requirements can often result in excessive P application. A greenhouse bioassay study was conducted to evaluate bioavailable P from biosolid and manure amendments and to determine the effectiveness of the modified Morgan soil test (pH 4.8, 1.25 M ammonium acetate) and an in situ anion exchange membrane resin P soil test (PInSitu) to estimate plant-available P in the amended soil. The effects of biosolid stabilization processes on P availability were investigated by using lime stabilized (LSB), composted (CB), anaerobically digested (ADB) and unstabilized (UB) biosolids. The three animal manures studied were: dairy (DM), poultry (PM), and swine (SM). Triple super phosphate (TSP) served as an inorganic reference. Cumulative net P uptake by ryegrass (Lolium perenne L.) was highest for DM and SM, intermediate for PM, LSB, UB and TSP, and lowest for CB and ADB. Soil test P levels measured by the Morgan and PAEM methods were highly correlated (r = 0.88, p = 0.01). The P uptake by ryegrass (Lolium perenne L.) agreed well with predicted P availability, indicating that both the modified Morgan soil test and in situ exchange resin methods are appropriate for determining P availability in biosolid- and manure-amended agricultural soils.